class_docstr: AVA Dataset
class_docstr_tok: ["AVA","Dataset"]
docstr: Returns:
      (int): the number of videos in the dataset.
docstr_tok: ["Returns",":","(","int",")",":","the","number","of","videos","in","the","dataset","."]
code: def num_videos(self):
      """
      Returns:
          (int): the number of videos in the dataset.
      """
      return len(self._keyframe_indices)
  
file_path: SlowFast/slowfast/datasets/ava_dataset.py
imports: import logging
  import numpy
  import torch
  from .None import ava_helper
  from .None import cv2_transform
  from .None import transform
  from .None import utils
  from .build import DATASET_REGISTRY
label_desc: Use image node_id 5 for calling the Ava obj's underlying member method code with example usage: obj.num_videos() and returns: len